When we talk about riding position we say it should be in neutral but do we mean it should stay there throughout every beat of every stride?
When we ride we move with the horse which means our pelvis and spine are constantly moving to absorb and re-stabilise.
This means stability is not stiff, it is not tense or rigid.
It is the ability to stay balanced whilst absorbing force and going with movement in a relaxed frame. The Spine and Pelvis will gently rock forward, back, up, down and even side to side but in very good riders this will be almost invisible. Yet we all know to do that on top of half a ton of animal is much easier said than done.
What does this mean for our training?
It means that we need to incorporate some of this fluid movement into our off horse training.
We need to learn how to move the Pelvis and Spine in and out of neutral whilst remaining stable throughout.
Now to achieve the strength and control to do this may start with building static strength and body control.
Once we have that we need to advance this to staying stable whilst moving so for example static may be a Wall Squat, moving may be a Squat and then more Dynamic a Squat Jump. The idea being that throughout the Squat and Squat Jump the position does not change wildly it merely adjust subtlety to absorb the landing.
Perhaps for a more visually and kinesthetic (feeling) exercise sit on a gym ball starting from neutral and start to bounce as if advancing a trot, add in your seat bones following the front legs of that trot and start to make that trot bigger. The whole time you should feel that to remain rigid prevents you from being fully in sync with the ball whereas if you allow your spine and pelvis to move you can stay with the ball whilst still remaining in balance.
This involves you learning which muscles are required and what level of tension is needed in these muscles to achieve this. It relies on your own feel and is therefore a really good learning exercise for riding in general.
Give it a go and see what you feel.